// NameFilter.cs
//
// Copyright 2005 John Reilly
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

using System;
using System.Collections;
using System.Text.RegularExpressions;

namespace _videoConference.ZipUnzip.Core
{
    /// <summary>
    /// NameFilter is a string matching class which allows for both positive and negative
    /// matching.
    /// A filter is a sequence of independant <see cref="Regex">regular expressions</see> separated by semi-colons ';'
    /// Each expression can be prefixed by a plus '+' sign or a minus '-' sign to denote the expression
    /// is intended to include or exclude names.  If neither a plus or minus sign is found include is the default
    /// A given name is tested for inclusion before checking exclusions.  Only names matching an include spec 
    /// and not matching an exclude spec are deemed to match the filter.
    /// An empty filter matches any name.
    /// </summary>
    /// <example>The following expression includes all name ending in '.dat' with the exception of 'dummy.dat'
    /// "+\.dat$;-^dummy\.dat$"
    /// </example>
    public class NameFilter : IScanFilter
    {
        /// <summary>
        /// Construct an instance based on the filter expression passed
        /// </summary>
        /// <param name="filter">The filter expression.</param>
        public NameFilter(string filter)
        {
            filter_ = filter;
            inclusions_ = new ArrayList();
            exclusions_ = new ArrayList();
            Compile();
        }

        /// <summary>
        /// Test a string to see if it is a valid regular expression.
        /// </summary>
        /// <param name="expression">The expression to test.</param>
        /// <returns>True if expression is a valid <see cref="System.Text.RegularExpressions.Regex"/> false otherwise.</returns>
        public static bool IsValidExpression(string expression)
        {
            bool result = true;
            try
            {
                Regex exp = new Regex(expression, RegexOptions.IgnoreCase | RegexOptions.Singleline);
            }
            catch
            {
                result = false;
            }
            return result;
        }

        /// <summary>
        /// Test an expression to see if it is valid as a filter.
        /// </summary>
        /// <param name="toTest">The filter expression to test.</param>
        /// <returns>True if the expression is valid, false otherwise.</returns>
        public static bool IsValidFilterExpression(string toTest)
        {
			if ( toTest == null )
			{
				throw new ArgumentNullException("toTest");
			}

            bool result = true;

            try
            {
                string[] items = toTest.Split(';');
                for ( int i = 0; i < items.Length; ++i )
                {
                    if ( items[i] != null && items[i].Length > 0 )
                    {
                        string toCompile;

                        if ( items[i][0] == '+' )
                        {
                            toCompile = items[i].Substring(1, items[i].Length - 1);
                        }
                        else if ( items[i][0] == '-' )
                        {
                            toCompile = items[i].Substring(1, items[i].Length - 1);
                        }
                        else
                        {
                            toCompile = items[i];
                        }

                        Regex testRegex = new Regex(toCompile, RegexOptions.IgnoreCase | RegexOptions.Singleline);
                    }
                }
            }
            catch ( Exception )
            {
                result = false;
            }

            return result;
        }

        /// <summary>
        /// Convert this filter to its string equivalent.
        /// </summary>
        /// <returns>The string equivalent for this filter.</returns>
        public override string ToString()
        {
            return filter_;
        }

        /// <summary>
        /// Test a value to see if it is included by the filter.
        /// </summary>
        /// <param name="name">The value to test.</param>
        /// <returns>True if the value is included, false otherwise.</returns>
        public bool IsIncluded(string name)
        {
            bool result = false;
            if ( inclusions_.Count == 0 )
            {
                result = true;
            }
            else
            {
                foreach ( Regex r in inclusions_ )
                {
                    if ( r.IsMatch(name) )
                    {
                        result = true;
                        break;
                    }
                }
            }
            return result;
        }

        /// <summary>
        /// Test a value to see if it is excluded by the filter.
        /// </summary>
        /// <param name="name">The value to test.</param>
        /// <returns>True if the value is excluded, false otherwise.</returns>
        public bool IsExcluded(string name)
        {
            bool result = false;
            foreach ( Regex r in exclusions_ )
            {
                if ( r.IsMatch(name) )
                {
                    result = true;
                    break;
                }
            }
            return result;
        }

        /// <summary>
        /// Test a value to see if it matches the filter.
        /// </summary>
        /// <param name="name">The value to test.</param>
        /// <returns>True if the value matches, false otherwise.</returns>
        public bool IsMatch(string name)
        {
            return (IsIncluded(name) == true) && (IsExcluded(name) == false);
        }

        /// <summary>
        /// Compile this filter.
        /// </summary>
        void Compile()
        {
            // TODO: Check too see if combining RE's makes it faster/smaller.
            // simple scheme would be to have one RE for inclusion and one for exclusion.
            if ( filter_ == null )
            {
                return;
            }

            // TODO: Allow for paths to include ';'
            string[] items = filter_.Split(';');
            for ( int i = 0; i < items.Length; ++i )
            {
                if ( (items[i] != null) && (items[i].Length > 0) )
                {
                    bool include = (items[i][0] != '-');
                    string toCompile;

                    if ( items[i][0] == '+' )
                    {
                        toCompile = items[i].Substring(1, items[i].Length - 1);
                    }
                    else if ( items[i][0] == '-' )
                    {
                        toCompile = items[i].Substring(1, items[i].Length - 1);
                    }
                    else
                    {
                        toCompile = items[i];
                    }

                    // NOTE: Regular expressions can fail to compile here for a number of reasons that cause an exception
                    // these are left unhandled here as the caller is responsible for ensuring all is valid.
                    // several functions IsValidFilterExpression and IsValidExpression are provided for such checking
                    if ( include )
                    {
                        inclusions_.Add(new Regex(toCompile, RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.Singleline));
                    }
                    else
                    {
                        exclusions_.Add(new Regex(toCompile, RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.Singleline));
                    }
                }
            }
        }

        #region Instance Fields
        string filter_;
        ArrayList inclusions_;
        ArrayList exclusions_;
        #endregion
    }
}
